System for the chemical decontamination of corrosive gases

ABSTRACT

The use of a composition including at least one acido-basic neutralising agent for decontaminating an atmosphere contaminated by a corrosive gas, the acido-basic neutralising agent having at least 2 pKa&#39;s and being characterised by: pKa 1≤pKa 2, pKa 1&gt;2, pKa 2&lt;12, 4&lt;½ (pKa 1+pKa 2)&lt;10 pKa 1, representing the smallest of the basic pKa&#39;s and pKa 2 representing the largest of the acidic pKa&#39;s. Also, a method for decontaminating an atmosphere contaminated by a corrosive gas comprising the spraying of the neutralising agent, and to a decontamination device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/791,774, filed on Jul. 8, 2022, which is a continuation ofInternational Application No. PCT/FR2021/050029, filed on Jan. 8, 2021,which claims priority to French Patent Application No. FR2000212, filedon Jan. 10, 2020. All of the aforementioned patent applications arehereby incorporated by reference in their entireties.

FIELD

The invention relates to the field of the chemical decontamination of anatmosphere. More precisely, it relates to the use of a compositioncomprising an acido-basic neutralising agent for decontaminating anatmosphere contaminated by a corrosive gas. The present invention alsorelates to a decontamination method comprising said composition.

BACKGROUND

Chemical contamination of an atmosphere by corrosive acid or base gasesmay occur during chemical accidents, for example when pipes or cylinderscontaining corrosive gases are damaged or pierced.

Chemical contamination of an atmosphere may also occur during leaks orspillages of liquid chemical products emitting corrosive vapours.

In such cases, the surrounding atmosphere is then contaminated by thesecorrosive gases or vapours.

A person skilled in the art then has only a few options fordecontaminating the atmosphere and to make it secure and once againsuitable for work.

When this chemical contamination takes place in a closed space, it ispossible to ventilate, via openings to the outside to discharge thecontaminant, i.e. the corrosive gases or vapours. Such a solution has anecological drawback since this entrains the chemical contaminant to theoutside and then causes environmental pollution. On the other hand, sucha solution is not applicable in the case of a space with no openings tothe outside.

If the space is provided with a forced ventilation system, it ispossible to aspirate the contaminated air and to pass it through afilter in which the contaminant will be trapped. However, this requiresexpensive equipment for the building upstream in the case of potentialincidents.

During fires emitting harmful or corrosive gases, it is fairly frequentfor fire-fighters to produce a curtain of water so as to dissolve thegases in the water and thus prevent propagation thereof. However, theconsequence of this is generating a large quantity of contaminatedliquid waste and completely flooding the area affected.

Apart from the use of natural elements, chemical decontamination methodshave been developed for decontaminating an atmosphere.

Thus, in the case of biological contamination of the atmosphere, forexample by microorganisms, decontamination systems based on the sprayinginto the area of a solution of ozone, of peracetic acid (WO2018/143186)or of dry hydrogen peroxide (WO2019/133801) can be used.

When the contamination of the atmosphere is due to an organic compound,there are systems for injecting gaseous methanol put in contact with acatalyst to transform it into hydroxyl, hydroperoxy or hydroxymethylradicals that will then react with the organic compound to make itnon-toxic (WO2013/137452). These systems require the use of methanol andof radicals harmful to the health and make it possible only to degradevolatile compounds.

During a chemical contamination, decontamination solutions have beendeveloped for cases where the contaminant is in liquid or solid form.

Thus chloro-oxidising solutions based on hypochlorite ions ClO⁻ orhypochloric acid HClO were developed for decontaminating formaldehyderesidues (WO2019/150301).

It has also been shown that gaseous ozone made it possible todecontaminate overalls of fire-fighters contaminated by carcinogenicproducts resulting from combustion during a fire (WO 2019/113434). Fordecontaminating overalls contaminated by polycyclic aromatichydrocarbons such as benzo(a)pyrene, solutions or liquid dispersionsbased on cerium salts in water were developed (WO2019/112571).

Mention can also be made of reactive chemical absorbents based onsilica, active carbon and zeolite for contaminating warfare chemicalagents in liquid form (patent EP3476474).

Physiological solutions based on complexed amphoteric agents have alsobeen described for decontaminating parts of the human or animal bodycontaminated by a corrosive or irritant product.

It was therefore necessary to develop a method for decontaminating anatmosphere contaminated by corrosive gases based on the use of productsthat are non-toxic for humans, that are easy to use and that make itpossible to avoid the propagation of the contamination in theenvironment.

SUMMARY

The present invention relates to the use of a composition comprising atleast one acido-basic neutralising agent for decontaminating anatmosphere contaminated by a corrosive gas, said acido-basicneutralising agent having at least 2 pKa's and being characterised inthat:

pKa 1≤pKa 2

pKa 1>2

pKa 2<12

4<½(pKa 1+pKa 2)<10

pKa 1 representing the smallest of the basic pKa's and pKa 2representing the largest of the acidic pKa's.

Within the meaning of the present application, “corrosive gas” means agas causing corrosion in contact therewith, i.e. an alteration to amaterial or alterations to the skin when it is a case of living beings(irritations, chemical lesions, for example) through its acidic or basiccharacter. Within the meaning of the present invention, the term“corrosive gas” encompasses corrosive vapours emitted by certain liquidchemical products. Thus, within the meaning of the invention, corrosivegases include acids and bases. By way of example, mention can be made ofammonia (NH₃), hydrogen chloride (HCl), sulphur trioxide and hydrogenfluoride, hydrogen iodide, acetic acid, hydrogen sulphide, hydrogencyanide. Corrosive gases also include gaseous chemical products which,in contact with the moisture of the air or of the skin, hydrolyse intoan acid or into a base, such as dibromium (Br2), which hydrolyses intohydrogen bromide (HBr), a toxic and highly corrosive colourless gas.Corrosive gases also include volatile amines, such as ethanolamines suchas for example tiethanolamine and alkylamines such as for examplediethylamine.

“Atmosphere” means an atmosphere of a location able to receive humans oranimals such as for example a warehouse, a hangar, a building or a room.

A contaminated atmosphere may occur in the case of a chemical accidentwith a gas leak or during leaks or spillages of liquid chemical productsemitting corrosive vapours. In such cases, the surrounding atmosphere isthen contaminated by these corrosive gases or vapours.

The composition according to the invention makes it possible todecontaminate large volumes of atmosphere, such as in the case ofcontamination of a room, warehouse or building. In this, the compositionis effective for treating a substantial rate of gas to decontaminatesuch large atmospheres. By way of example, a 1000 m² warehouse and 6 mhigh (conventional warehouse) can be decontaminated in 5 min, at atreatment rate of 72,000 m³/h of contaminated air with the compositionaccording to the invention.

In addition, the composition according to the invention allows for adecontamination without knowing the parameters of the contaminating gasin question (source of emission, concentration, rate, nature).

“Decontamination” means that the concentration in corrosive gas in theatmosphere has fallen to the threshold or below regulatory values forlong-term exposure such as the occupational exposure limits (OELs)defined by the directives of the European Union. In this regard, mentioncan be made of Directives 98/24/EC, 2000/39/EC, 2006/15/EC, 2009/161/EU,(EU) 2017/164, 2004/37/EC, (UE) 2017/2398 and (UE) 2019/130.

The value of the regulatory threshold will depend on the nature of thegas.

Table 1 hereinbelow provides the exposure limit value not to be exceededfor an exposure of 8 h, for certain corrosive gases. These values weredefined by European or national directives.

TABLE 1 Exposure limit value (ppm) not to be exceeded for an exposure of8 h for certain corrosive gases Exposure limit Corrosive gas value (ppm)Ammonia (NH₃) 20 Hydrogen chloride (HCl) 5 Sulphur trioxide 5 Hydrogenfluoride (HF) 1.8 Hydrogen iodide 0.01 Acetic acid 10 Hydrogen sulphide5 Hydrogen cyanide 0.9 Hydrogen bromide (HBr) 2 Ethanolamines(Triethanolamine) 0.5 Alkylamines (Diethylamine) 5

The exposure limit values not to be exceeded for an exposure of 8 haccording to the chemical species may be found on the website of the IFA(Institute for Occupational Safety and Health of the German SocialAccident Insurance) at the following address:https://limitvalue.ifa.dguv.de/

Thus, in a particular embodiment, “decontamination” means that theconcentration in corrosive gas in the atmosphere is less than or equalto 20 ppm, in particular less than or equal to 10 ppm, more particularlyless than or equal to 5 ppm, even more particularly less than or equalto 1 ppm.

“Decontamination” means that the concentration in corrosive gas in theatmosphere was reduced by at least 70%, in particular by at least 90%,more particularly by at least 95%.

The decontamination may also be appreciated by toxicological values byinhalation such as the Derived no effect level (DNEL) by inhalation overthe long term. The latter are provided in the REACH registrationdossiers of substances following the tests conducted.

The decontamination may also be appreciated by a pH of the residuesbetween 4 and 9, for example with a coloured indicator or a pH-meter.

In a particular embodiment, said acido-basic neutralising agent is abuffer solution and is characterised in that:

pKa 1=pKa 2

pKa 1>2

pKa 2<12

4<½(pKa 1+pKa 2)<10,

pKa 1 representing the smallest of the basic pKa's and pKa 2representing the largest of the acidic pKa's.

In a particular embodiment, said acido-basic neutralising agent ischaracterised in that:

pKa 1<pKa 2

pKa 1>2

pKa 2<12

4<½(pKa 1+pKa 2)<10,

pKa 1 representing the smallest of the basic pKa's and pKa 2representing the largest of the acidic pKa's.

In a particular embodiment, said acido-basic neutralising agent is anamphoteric agent.

Within the meaning of the present application, “amphoteric agent” meansa chemical species possessing both the acidic function and the basicfunction and consequently having at least two dissociation constants(pKa), one corresponding to the acid function and the othercorresponding to the basic function.

Typically, the amphoteric agent is selected from the group consistingof: an amino acid or an amino acid salt, a citric acid salt, aphosphoric acid salt, a pyrophosphoric acid salt, anethylenediaminetetraacetic acid (EDTA) salt, complexed or free, anascorbic acid salt, or a carbonate.

In a particular embodiment, the amphoteric agent is an ascorbic acidsalt, for example sodium ascorbate.

In a particular embodiment, the amphoteric agent is an amino acid, forexample L-alanine.

In a particular embodiment, the amphoteric agent is an EDTA salt, forexample EDTA disodium.

In a particular embodiment, the amphoteric agent is an amino acid salt,more particularly a glutamate salt, for example sodium glutamate.

In a particular embodiment, the amphoteric agent is a carbonate, moreparticularly a hydrogencarbonate, in particular sodiumhydrogencarbonate.

In a particular embodiment, the amphoteric agent is used at aconcentration of at least 0.01 mol/L and within the limit of solubilityof the amphoteric agent. For example, it is used at a concentration ofbetween 0.01 mol/L and 10 mol/L, in particular between 0.1 and 5 mol/L,more particularly between 0.1 and 2 mol/L, even more particularly at 1mol/L or 0.5 mol/L.

In a particular embodiment, the composition contains two amphotericagents, as defined previously.

In a particular embodiment, the two amphoteric agents are a complexedEDTA salt such as an EDTA-aluminium disodium complex, and an amino acidsalt, more particularly a glutamate salt, for example sodium glutamate.

In a particular embodiment, said acido-basic neutralising agent is amixture of at least one conjugate base of an acid and at least oneconjugate acid of a base.

Typically, the conjugate base and the conjugate acid are used at aconcentration of at least 0.01 mol/L and within the limit of theirsolubility. For example, they are used at a concentration of between0.01 mol/L and 10 mol/L, in particular between 0.1 mol/L and 5 mol/L,more particularly 1 mol/L or 0.5 mol/L.

In one embodiment, said conjugate acid and said conjugate base arepresent in an equimolar ratio.

In a particular embodiment, said conjugate base is an EDTA-aluminiumdisodium complex and the conjugate acid is boric acid.

Within the meaning of the present application, “EDTA-aluminium disodiumcomplex” means a disodium salt of a complex based on aluminium andethylenediaminetetraacetic acid having the general formula [Al(Y)Bn]c′Dcwith B representing OH⁻, BO²⁻, H⁺, Y representing a tetracarboxylatethat can be protonated four times to form ethylenediaminetetraaceticacid, n representing an integer number equal to 0, 1, 2 or 3, D being acounter-ion, preferably Na+, c being an integer number equal to 2 and c′being a relative number having the same absolute value as c.

In one embodiment, the acido-basic neutralising agent makes it possibleto chelate ligands, in particular fluoride ions. This is because somegases can release ions having a toxic effect on the organism. Such isthe case with fluoride ions, which can come in particular from gaseoushydrogen fluoride, which bind to the calcium and to the magnesium of theorganism when inhaled, and can thus cause systemic malfunctioning thatcan lead to cardiac arrest.

Thus, in a particular embodiment, the neutralising agent haselectrophilic properties so that the fluoride ion F⁻ can fix thereon.The bond between the electrophilic neutralising agent and F⁻ must bestronger than that between F⁻ and Ca²⁺ or F⁻ and Mg²⁺ so that F⁻preferentially binds to the electrophilic neutralising agent and not tothe calcium or magnesium of the human body.

A person skilled in the art is able without difficulty to select aneutralising agent as defined above and having strength allowing a bondwith a fluoride ion that is stronger than that between a fluoride ionand Ca²⁺ and that between a fluoride ion and Mg²⁺.

Furthermore, the composition according to the present invention maycomprise at least one additive selected from surfactants, pH indicators,preservatives, and mixtures thereof. A person skilled in the art is ableto select, from all these possible additives, both the composition andthe quantity of those that will be added to the composition, so that thelatter keeps all its properties.

Within the meaning of the present application, “surfactant” means anagent for stabilising the composition or allowing mixing thereof with anorganic solvent.

The surfactant may be hydrophobic with an HLB of 3 to 10 or hydrophilicwith an HLB of 11 to 18. The HLB (from the English “hydrophiliclipophilic balance”) of the surfactant or of the mixture of surfactantswill be determined by the Griffin method (Griffin WC: Classification ofSurface-Active Agents by ‘HLB’, Journal of the Society of CosmeticChemists 1 (1949): 311. Griffin WC: Calculation of HLB Values ofNon-Ionic Surfactants, Journal of the Society of Cosmetic Chemists 5(1954): 259).

Examples of surfactants are ethoxylated fatty alcohols, fatty acids andesters (for example: ceteareth-12, ceteareth-20, ceteareth-33,ethoxylated (20 moles) cetyl stearyl alcohol, polyglyceryl-2polyhydroxystearate, glyceryl oleate, sorbitan ester, glycerol ester,PEG-mono/di-laurate, PEG-mono/di-stearate, cetearyl isononanoate,glyceryl stearate, etc), carboxylates, ethoxy carboxylates (for example:sodium/potassium stearate, alkyl-carboxylic acid, alkyl-polyglycol ethercarboxylic acid, alkylphenol polyglycol ether carboxylic acid,carboxymethylated alcohol, ethoxy carboxylate, ether carboxylate, etc.),octoxynol, capryl caprilyl glucoside, and mixtures thereof.

In one embodiment, the composition according to the invention comprisesa quantity of surfactant of 0.1% to 10% by weight, preferably 0.5 to 5%by weight, and more preferentially still from 1 to 3% by weight of thetotal weight of the composition.

Within the meaning of the present application, “pH indicator” means acompound that has the ability to change colour according to the pH ofits surrounding environment.

Examples of pH indicators are thymol blue, tropaeolin, bromocresolpurple, bromophenol blue, Congo red, neutral red, phenolphthalein,thymolphthalein, alizarin yellow R, bromothymol blue, cresol red, methylviolet, malachite green, methyl yellow, Congo red, methyl orange,bromocresol green, methyl red, phenol red, alizarin, indigo carmine andmixtures thereof.

The presence of a pH indicator makes it possible to view the completeneutralisation of the gas to be depolluted, using the correct quantityof composition necessary, and thus to reduce the cost ofdecontamination.

Within the meaning of the present application, “preservative” means anagent for limiting the development of microorganisms within thecomposition. More particularly they make it possible to stop or inhibitthe growth of microorganisms. The concentrations used arebacteriostatic. The combination of an antibacterial (ATB) and anantifungal agent (ATF) may be necessary.

Thus, adding at least one preservative makes it possible to obtain acomposition not allowing the growth and multiplication of bacteria,fungi and/or mould.

Examples of preservatives are para-hydroxybenzoic alkyl ester,isothiazolinone, imidazolidinyl urea, diazolidinyl urea, methylparaben,propylparaben, propylene glycol, bromo-nitro-propanediol,phenoxyethanol, sorbic acid and salts thereof, benzoic acid and saltsthereof, phenoxyethanol, benzyl alcohol, and mixtures thereof. Thesecompounds are generally between 0.01% and 0.5% of the total weight ofthe composition.

In order to prevent or limit the development of microorganisms, thecomposition may also be a sterile composition. A sterile composition canbe obtained according to methods well known to a person skilled in theart. It is next stored under sterile conditions until use.

In a particular embodiment, said composition is in the form of asolution, also called liquid.

The composition may be in the form of an aqueous solution. Inparticular, said composition comprises from 20% to 99.9% water, moreparticularly 60 to 95%%, typically 75%.

The composition may also be in solution in an organic solvent. Inparticular, said composition comprises from 20 to 99.9% organic solvent,more particularly 60 to 95%, typically 75%.

By way of example, the organic solvent may be a fatty acid ester, alinear alkane, a cyclic alkane, a glycol ether or a glycol ether ester.

In an embodiment, said composition in the form of a solution isformulated in the form of a foam.

In one embodiment, said composition is in solid form. In particular, itmay be in the form of solid particles, also referred to as powder. Thepowder may be diluted in a neutral powder.

In one embodiment, said composition in solution form or in solid formmay be formulated in aerosol form.

Within the meaning of the present application, “aerosol” means that thecomposition is in the form of a colloid of liquid drops in suspension ina carrier gas or that it is in the form of a colloid of solid particlesin suspension in a carrier gas. Typically, the carrier gas is a neutralgas such as nitrogen, air or compressed air.

In one embodiment, the composition according to the invention describedabove is sprayed directly into the atmosphere contaminated by corrosivegases.

The present invention also relates to a method for decontaminating anatmosphere contaminated by a corrosive gas comprising the followingsteps:

-   -   1) spraying, directly into the contaminated atmosphere, a        composition comprising at least one acido-basic neutralising        agent for decontaminating an atmosphere contaminated by a        corrosive gas, said acido-basic neutralising agent having at        least 2 pKa's and being characterised in that:

pKa 1≤pKa 2

pKa 1>2

pKa 2<12

4<½(pKa 1+pKa 2)<10

pKa 1 representing the smallest of the basic pKa's and pKa 2representing the largest of the acidic pKa's; then

-   -   2) checking the decontamination;    -   3) optionally repeating steps 1 and 2 until there is total        decontamination;    -   4) recovering the solid or liquid residues;    -   5) optionally rinsing the decontaminated zone to eliminate the        residues of the composition.

In one embodiment of the method, step 1) is triggered manually.

In one embodiment of the method, step 1) is triggered automatically.

Step 1) may be preceded by detecting a gas in the atmosphere, inparticular via a gas-detection system.

In a particular embodiment, said acido-basic neutralising agent used atstep 1) is a buffer solution and is characterised in that:

pKa 1=pKa 2

pKa 1>2

pKa 2<12

4<½(pKa 1+pKa 2)<10,

pKa 1 representing the smallest of the basic pKa's and pKa 2representing the largest of the acidic pKa's.

In a particular embodiment, said acido-basic neutralising agent used atstep 1) is characterised in that:

pKa 1<pKa 2

pKa 1>2

pKa 2<12

4<½(pKa 1+pKa 2)<10,

pKa 1 representing the smallest of the basic pKa's and pKa 2representing the largest of the acidic pKa's.

In a particular embodiment, said acido-basic neutralising agent used atstep 1) is an amphoteric agent. In particular, the amphoteric agent isselected from the group consisting of: an amino acid or an amino acidsalt, a citric acid salt, a phosphoric acid salt, a pyrophosphoric acidsalt, an ethylenediaminetetraacetic acid (EDTA) acid salt, complexed orfree, an ascorbic acid salt, or a carbonate.

In a particular embodiment, the amphoteric agent is an ascorbic acidsalt, for example sodium ascorbate.

In a particular embodiment, the amphoteric agent is an amino acid, forexample L-alanine.

In a particular embodiment, the amphoteric agent is an EDTA salt, forexample EDTA disodium.

In a particular embodiment, the amphoteric agent is an amino acid salt,more particularly a glutamate salt, for example sodium glutamate.

In a particular embodiment, the amphoteric agent is a carbonate, moreparticularly a hydrogencarbonate, in particular sodiumhydrogencarbonate.

In a particular embodiment, the amphoteric agent is used at aconcentration of at least 0.01 mol/L and within the soluble limit of theamphoteric agent. For example, it is used at a concentration of 0.01mol/L and 10 mol/L, in particular between 0.1 and 5 mol/L, moreparticularly between 0.1 and 2 mol/L, even more particularly at 1 mol/Lor 0.5 mol/L.

In a particular embodiment, the composition contains two amphotericagents. In particular, the two amphoteric agents are a complexed EDTAsalt such as an EDTA-aluminium disodium complex, and an amino acid salt,more particularly a glutamate salt, for example sodium glutamate.

In a particular embodiment, said acido-basic neutralising agent used atstep 1) is a mixture of at least one conjugate base of an acid and atleast one conjugate acid of a base.

Typically, the conjugate base and the conjugate acid are used at aconcentration of at least 0.01 mol/L and in the limit of theirsolubility. For example, they are used at a concentration of between0.01 mol/L and 10 mol/L, in particular between 0.1 mol/L and 5 mol/L,more particularly 1 mol/L or 0.5 mol/L.

In one embodiment, said conjugate acid and said conjugate base arepresent in an equimolar ratio.

In a particular embodiment, said conjugate base is an EDTA-aluminiumdisodium complex and the conjugate acid is boric acid.

In one embodiment, the acido-basic neutralising agent used at step 1)has the possibility of chelating ligands, in particular fluoride ions.

Furthermore, the composition used at step 1) may optionally contain atleast one additive selected from surfactants, pH indicators,preservatives, and mixtures thereof, as defined in the presentapplication.

In order to prevent or limit the developments of microorganisms, thecomposition may also be a sterile composition, sterilised in accordancewith methods well known to a person skilled in the art.

In one embodiment, the composition used at step 1) is in the form of asolution, such as an aqueous solution, or in a solution in an organicsolvent.

In one embodiment, it may also be in solid form, in particular in powderform.

In a particular embodiment, the composition is sprayed in the form of asolution, in solid form, for example powder, in powder form, in foamform and/or in aerosol form.

The composition may be sprayed by means of a sprinkler, also referred toas a spray nozzle.

The composition may also be sprayed by means of an atomisation nozzle,which makes it possible to create a mist.

The composition may also be sprayed by means of a spray.

A person skilled in the art knows how to adapt the spray means accordingto the form of the composition.

A person skilled in the art also knows how to adapt the rate of thespray according to the shape of the room, the ceiling height and thevolume to be decontaminated.

Step 2 is a step of verifying the decontamination. For example, this maybe done by measuring the concentration in contaminating gas (in ppm) inthe atmosphere (gas detector), and/or by check of the pH of theresidues. If the composition of the invention comprises a pH indicator,the check on the pH of step 2) can be done visually by means of thecoloured indicators, and it is no longer necessary to measure the pH byanother method such as with a pH meter or the use of a pH paper. A pH ofthe residues between 4 and 9 is an indicator of effectivedecontamination.

Step 4) consists in recovering the solid or liquid residues. Once aresidue is obtained, the residue is collected with means normally usedby a person skilled in the art, for example using a shovel or a brush, ascraper or by suction according to the solid or liquid state of theresidue. A person skilled in the art knows how to adapt the means ofcollection according to the nature of the residue. Once of theadvantages of the invention is therefore an easy recovery of thedecontamination residues using everyday utensils.

In particular, it is a case of liquid residues.

One of the advantages of the composition according to the invention isthat the residues coming from the decontamination are at a pH between 4and 9. They are therefore not corrosive for the contaminated premisesand non-irritant and non-toxic for the persons in charge of recoveringthem. The elimination thereof therefore does not require specific andexpensive equipment.

The composition makes it possible to neutralise the corrosive gases witha use of a minimum quantity of product and at a lower cost compared withthe products of the prior art. In addition, the composition of thepresent invention has the advantage of not being dangerous for livingorganisms: it is non-toxic, non-irritant, non-allergenic, andnon-ecotoxic), unlike the products of the prior art.

Optionally, a rinsing of the decontaminated area to eliminate theresidues of the composition can be implemented as a last step.

The present invention also relates to a device for decontaminating anatmosphere contaminated by a corrosive gas, comprising at least onemeans 1 able to spray a composition comprising a least one acido-basicneutralising agent for decontaminating an atmosphere contaminated by acorrosive gas, said acido-basic neutralising agent having at least 2pKa's and being characterised in that:

pKa 1≤pKa 2

pKa 1>2

pKa 2<12

4<½(pKa 1+pKa 2)<10

pKa 1 representing the smallest of the basic pKa's and pKa 2representing the largest of the acidic pKa's, and at least one reservoir3 intended to receive said composition.

Within the meaning of the present application, “at least one” means one,two, three; for or more.

Typically, said composition is a composition as defined above in thepresent application.

As defined hereinabove, the composition may be in liquid, solid oraerosol form.

The means 1 able to spray the composition may be a spray, an atomisationnozzle, a foam generator or a sprinkler.

In a particular embodiment, the device comprises two reservoirs 3, eachone intended to receive the composition in a different form. In such anembodiment, the device therefore comprises two means 1 able to spray thecomposition, respectively adapted according to the form under which thecomposition has to be sprayed.

In a more particular embodiment, the device comprises:

-   -   a first reservoir intended to receive the composition in solid        form, connected to a means able to spray the composition in        powder form, and    -   a second reservoir intended to receive the composition in liquid        form, connected to a means able to spray the composition in        liquid or foam form.

The device may be a portable device. “Portable” means that the devicecan be moved by a person.

Alternatively, the device may be a fixed device. “Fixed” means that thedevice cannot be moved by a person. It is a case for example of a deviceintegrated in a building.

In one embodiment of a fixed device, said at least one spray means 1 isconnected to at least one circuit 2 comprising a fluid, said at leastone circuit 2 itself being connected to said at least one reservoir 3intended to receive the composition, by means of a valve 4. Actuatingthis valve 4 located at the junction of the reservoir 3 and of thecircuit 2 then allows release of the composition into the circuit, andthen spraying thereof through the spray means 1.

In a particular embodiment, the valve 4 also makes it possible to adjustthe rate of release of the composition in a controlled quantity.

In a particular embodiment, the composition is in liquid form and thefluid in the circuit is a liquid, in particular water or watercomprising an antigel product.

In a particular embodiment, the composition is in solid form, inparticular in powder form, and the fluid in the circuit is a liquid, inparticular water or water comprising an antigel product.

In a particular embodiment, the composition is in solid form, inparticular in powder form, and the fluid in the circuit is a gas, inparticular a neutral gas such as nitrogen, air or compressed air.

In a particular embodiment, the composition is in aerosol form and thefluid in the circuit is a gas, in particular a neutral gas such asnitrogen, air or compressed air.

In a particular embodiment, the circuit 2 is a circuit belonging to afire-extinguishing plant. In other words, in this embodiment, thereservoir 3 is directly connected to the fire-extinguishing plant. Thisis because it is well known that such a plant comprises among otherthings a network of pipes, ending up at spray means, which can then alsobe used as a circuit 2 according to the present invention. Thisfire-extinguishing plant may be pre-existing in the structure in whichthe fixed device according to the present invention is installed.

Thus, in a particular embodiment, the decontamination device accordingto the present invention comprises at least one reservoir (3) connectedto at least one circuit (2) comprising a fluid, said at least onecircuit (2) being a circuit belonging to a fire-extinguishing plant.

In a particular embodiment, said valve 4 is coupled to a gas-detectionsystem 5 in particular via an automatic control unit 6. This allowsautomatic actuation thereof.

In a particular embodiment, a compartment is provided between thereservoir 3 and the valve 4. This compartment is intended to receivefirstly the fluid coming from the circuit 2 and secondly the compositioncoming from the reservoir 3, before release into the circuit 2.

When the composition is in liquid form, this compartment makes itpossible to dilute the composition before release into the circuit 2.

When said composition is in solid form, for example in powder form,dissolution or dilution of said composition then takes place in saidcompartment, prior to release thereof into the circuit 2.

It should be noted that the presence of this compartment is optional,the composition, in solid or liquid form, also being able to be directlyreleased into the circuit 2.

Examples of devices are presented in FIG. 1 and FIG. 2 .

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a device for decontaminating an atmosphere comprisingsprinklers 1 connected to a water circuit 2, itself being connected viaa valve 4 to a reservoir 3 able to receive a composition in aqueousform, said valve 4 being coupled to a gas detection system 5 via anautomatic control unit 6, for automatic actuation.

FIG. 2 shows a device for decontaminating an atmosphere comprisingsprinklers 1 connected to the water circuit 2, itself being connectedvia a valve 4 to a reservoir 3 able to receive a composition in solidform, by means of a valve 4 located at the junction of the reservoir 3and the water circuit 2, said valve 4 being coupled to a gas detectionsystem 5 via an automatic control unit 6, for automatic actuation.

FIG. 3 is a graph showing the change in the concentration in gaseous HCl(ppm) according to the volume (mL) sprayed of a composition comprising aEDTA-aluminium disodium complex and boric acid in an equimolar mixtureat 0.1 mol/L.

FIG. 4 is a graph showing the change in the concentration in gaseous HCl(ppm) according to the volume (mL) sprayed of a composition comprising aEDTA-aluminium disodium complex and sodium glutamate in an equimolarmixture at 0.5 mol/L.

FIG. 5 is a graph showing the change in the concentration in gaseous NH3(ppm) according to the volume (mL) sprayed of a composition comprising aEDTA-aluminium disodium complex and sodium glutamate in an equimolarmixture at 0.5 mol/L.

EXAMPLES Example 1

An aqueous chemical-decontamination composition is prepared, comprising,as neutralising agent, the following mixture:

-   -   a conjugate base of an acid: EDTA-aluminium disodium complex,        the pKa of which is 5.87 at a concentration of 0.1 mol/L, and    -   the conjugate acid of a base: boric acid the pKa of which is        9.28 at a concentration of 0.1 mol/L.

This composition is sprayed into an atmosphere contaminated by gaseousHCl, a corrosive acid, manually in an aerosol by a spray at a rate ofapproximately 175 mL/min and the carrier gas of which is compressed air.

After spraying the composition, the contaminated atmosphere wasdecontaminated and a contaminant content below the regulatory threshold(Average exposure value: 5 ppm) was obtained.

FIG. 3 shows the change in the concentration in Gaseous HCL according tothe volume of the composition sprayed into the atmosphere.

The pH of the liquid residue that falls out is 4, i.e. little acidic andnon-corrosive.

Example 2

An aqueous chemical-decontamination composition was prepared comprising,as neutralising agent, an amphoteric agent, sodium glutamate at aconcentration of 1 mol/L and the pKa's of which are 4.15 and 9.58. Thiscomposition is sprayed into an atmosphere contaminated by a corrosiveatmosphere, such as hydrogen chloride.

After spraying of the composition, the contaminated atmosphere wasdecontaminated and a level of contaminant below the regulatory thresholdwas obtained.

Example 3

An aqueous chemical decontamination composition is prepared comprisingas a neutralising agent, the following mixture:

-   -   a conjugate base of an acid: EDTA-aluminium disodium complex the        pKa of which is 5.87 at a concentration of 0.5 mol/L, et    -   the conjugate acid of a base: sodium glutamate the pKa of which        is 9.67 at a concentration of 0.5 mol/L.

This composition is sprayed via a pump in an atmosphere contaminated bygaseous HCl, a corrosive acid, manually as aerosol by a spray rate ofabout 375 m L/min.

After spraying the composition, the contaminated atmosphere wasdecontaminated and a content in contaminant below the regulatorythreshold (Average exposure value: 5 ppm) was obtained.

FIG. 4 shows the change in the concentration in Gaseous HCL according tothe volume of the composition sprayed into the atmosphere.

The pH of the liquid residue that falls out is 7, i.e. a neutral andnon-corrosive liquid.

Example 4

An aqueous chemical decontamination composition is prepared comprisingas a neutralising agent, the following mixture:

-   -   a conjugate base of an acid: EDTA-aluminium disodium complex the        pKa of which is 5.87 at a concentration of 0.5 mol/L, and    -   the conjugate acid of a base: sodium glutamate the pKa of which        is 9.67 at a concentration of 0.5 mol/L.

This composition is sprayed via a pump in an atmosphere contaminated bygaseous NH₃, a corrosive base, manually as aerosol by a spray rate ofabout 375 mL/min.

After spraying the composition, the contaminated atmosphere wasdecontaminated and a content in contaminant below the regulatorythreshold (Average exposure value: 20 ppm) was obtained.

FIG. 5 shows the change in the concentration in gaseous NH₃ according tothe volume of the composition sprayed into the atmosphere.

The pH of the liquid residue that falls out is between 7 and 8, i.e. aneutral and non-corrosive liquid.

1. A composition comprising at least one acido-basic neutralising agentfor decontaminating an atmosphere contaminated by a corrosive gas, saidat least one acido-basic neutralising agent being an amphoteric agentselected from the group consisting of: an amino acid or a salt of anamino acid, a citric acid salt, a phosphoric acid salt, a pyrophosphoricacid salt, an ethylenediaminetetraacetic acid (EDTA) salt, complexed orfree, and a carbonate, and said at least one acido-basic having at least2 pKa's, wherein:pKa 1≤pKa 2,pKa 1>2,pKa 2<12−4<½, and(pKa 1+pKa 2)<10, pKa 1 representing the smallest of the basic pKa's andpKa 2 represents the largest of the acidic pKa's.
 2. The compositionaccording to claim 1, wherein said composition is in solution form or insolid form.
 3. The composition according to claim 2, wherein saidcomposition in solution form or in solid form is formulated as anaerosol.
 4. The composition according to claim 2, wherein saidcomposition in solution form is formulated as a foam.
 5. The compositionaccording to claim 1, wherein said composition is sprayed directly intothe atmosphere contaminated by corrosive gases.
 6. The compositionaccording to claim 1, wherein said at least one acido-basic neutralisingagent is sodium glutamate.
 7. The composition according to claim 1,wherein said at least one acido-basic neutralising agent is L-alanine.8. The composition according to claim 1, wherein said at least oneacido-basic neutralising agent is EDTA disodium.
 9. The compositionaccording to claim 1, wherein said at least one acido-basic neutralisingagent is a hydrogencarbonate.
 10. The composition according to claim 9,wherein said at least one acido-basic neutralising agent is a sodiumhydrogencarbonate.
 11. A method for decontaminating an atmospherecontaminated by a corrosive gas comprising the following steps: 1)spraying, directly into the contaminated atmosphere, a compositioncomprising at least one acido-basic neutralising agent fordecontaminating an atmosphere contaminated by a corrosive gas, said atleast one acido-basic neutralising agent being an amphoteric agentselected from the group consisting of: an amino acid or a salt of anamino acid, a citric acid salt, a phosphoric acid salt, a pyrophosphoricacid salt, an ethylenediaminetetraacetic acid (EDTA) salt, complexed orfree, and a carbonate, and said at least one acido-basic having at least2 pKa's and wherein:pKa 1≤pKa 2,pKa 1>2,pKa 2<12−4<½, and(pKa 1+pKa 2)<10, pKa 1 representing the smallest of the basic pKa's andpKa 2 represents the largest of the acidic pKa's; then 2) checking thedecontamination; 3) optionally repeating steps 1 and 2 until there istotal decontamination; 4) recovering the solid or liquid residues; and5) optionally rinsing the decontaminated zone to eliminate the residuesof the composition.
 12. A device for decontaminating an atmospherecontaminated by a corrosive gas, comprising: at least one means able tospray a composition comprising at least one acido-basic neutralisingagent for decontaminating an atmosphere contaminated by a corrosive gas,said at least one acido-basic neutralising agent being an amphotericagent selected from the group consisting of: an amino acid or a salt ofan amino acid, a citric acid salt, a phosphoric acid salt, apyrophosphoric acid salt, an ethylenediaminetetraacetic acid (EDTA)salt, complexed or free, and a carbonate, and said at least oneacido-basic having at least 2 pKa's and wherein:pKa 1≤pKa 2,pKa 1>2,pKa 2<12−4<½, and(pKa 1+pKa 2)<10, pKa 1 representing the smallest of the basic pKa's andpKa 2 represents the largest of the acidic pKa's; and at least onereservoir intended to receive said composition.
 13. The device accordingto claim 12, wherein said at least one reservoir is connected to atleast one circuit comprising a fluid, said at least one circuit being acircuit belonging to a fire extinguishing plant.